Bacterial Translocation in Spondyloarthritis: Evaluation Before and After Starting a Biomedicine.

Axial spondyloarthritis is a common inflammatory rheumatic disease and its management is based on the use of NSAIDs and biotherapies (anti-TNF and anti-IL17 antibodies). Its pathophysiology involves the digestive mucosa. The colon of patients with spondyloarthritis is the site of asymptomatic inflammation. This inflammation results from dysbiosis, which is responsible for activation of innate immunity linked to bacterial translocation phenomena. Dendritic cells are then activated and the immune response is polarized towards the IL23/Th17 axis. This translocation is secondary to an increase in colonic permeability. The increase in digestive permeability allows translocation of bacteria or bacterial fragments, primarily lipopolysaccharide (LPS).

Some proinflammatory cytokines (TNF, IFNγ, and IL23) cause an increase in digestive permeability. IL17 produced in the digestive mucosa has two different effects. Indeed, two types of colonic T cells produce IL17: regulatory T Helpers 17 producing IL10 and IL17 and inflammatory T Helpers 17 producing IL17 and IFNγ.

The investigators hypothesize that biotherapies decrease bacterial translocation. They suspect a lesser effect of anti-IL17 compared to anti-TNF because of the potential inhibition of Treg17 lymphocytes.